Shujiro Minami

Mechanisms of noise-induced hearing loss indicate multiple methods of prevention.

Recent research has shown the essential role of reduced blood flow and free radical formation in the cochlea in noise-induced hearing loss (NIHL). The amount, distribution, and time course of free radical formation have been defined, including a clinically significant late formation 7-10 days following noise exposure, and one mechanism underlying noise-induced reduction in cochlear blood flow has finally been identified. These new insights have led to the formulation of new hypotheses regarding the molecular mechanisms of NIHL; and, from these, we have identified interventions that prevent NIHL, even with treatment onset delayed up to 3 days post-noise. It is essential to now assess the additive effects of agents intervening at different points in the cell death pathway to optimize treatment efficacy. Finding safe and effective interventions that attenuate NIHL will provide a compelling scientific rationale to justify human trials to eliminate this single major cause of acquired hearing loss.

Antioxidant protection in a new animal model of cisplatin-induced ototoxicity.

Mortality is a major complication in animal models of cisplatin-induced hearing loss due to the systemic toxicity of the drug. Here we report on a novel two-cycle treatment in rats, each cycle consisting of four days of cisplatin injections (1 mg/kg, i.p., twice daily) separated by 10 days of rest. This regimen, similar to clinical courses of cancer chemotherapy, produced significant hearing loss without mortality. Auditory brain stem evoked responses were unchanged after the first cycle but were elevated by 40-50 dB at 16 and 20 kHz after the second. Loss of outer hair cells occurred after the second cycle, predominantly in the base of the cochlea. Total cochlear antioxidants declined progressively during drug treatment and were reduced to 60% of control values after the second cisplatin cycle. Co-administration of salicylate (100 mg/kg, s.c., twice daily) during both cycles or during the second cycle restored antioxidant levels and reduced cisplatin-induced threshold shifts. This model of cisplatin ototoxicity without mortality eliminates potentially confounding factors that may determine the survival of a special cohort of animals. The results also support the notion that reactive oxygen species are involved in cisplatin ototoxicity and show the potential usefulness of antioxidant treatment.

Correlations of inflammatory biomarkers with the onset and prognosis of idiopathic sudden sensorineural hearing loss

Hypothesis We investigated whether inflammatory biomarkers and stress are involved in the pathophysiology of idiopathic sensorineural hearing loss (ISHL). Study Design Individual cohort study. Setting Two tertiary centers. Patients Forty-three ISHL and 10 non-ISHL patients seen in our ENT departments from 2004 to 2010 within a week from the onset of new symptoms and without steroid administration before visiting our departments. Intervention Multiple audiologic evaluations, blood tests including leukocyte counts, natural killer cell activity (NKCA), interleukin 6 (IL-6), tumor necrosis factor, high-sensitivity CRP (hCRP), and the General Health Questionnaire were used to evaluate the systemic stress and inflammatory response. Main Outcome Measures Correlations between biomarkers and ISHL severity and prognosis were evaluated by statistical analysis. Results In the ISHL patients, a neutrophil count above the reference range was associated with severe hearing loss and poor prognosis, and was accompanied by low NKCA and high IL-6. In the non-ISHL patients, these associations were not present. The abnormal neutrophil count was independent of preexisting vascular diseases. The abnormal counts responded to treatment and decreased into the reference range. Conclusion Neutrophil counts above the reference range of a facility will be a useful indicator of poor prognosis of ISHL. Synchronism of different types of NF-&kgr;B activation pathways could be required to cause severe ISHL. An NKCA decrease, an acute neutrophil count increase, and an IL-6 increase can induce NF-&kgr;B activation in the cochlea and cause severe ISHL. Further epidemiologic surveys should be conducted to evaluate whether stressful life events increase the risk of severe ISHL onset.

Calcineurin Activation Contributes to Noise-Induced Hearing Loss

Acoustic overstimulation increases Ca2+ concentration in auditory hair cells. Because calcineurin is known to activate cell death pathways and is controlled by Ca2+ and calmodulin, this study assessed the role of calcineurin in auditory hair cell death in guinea pigs after intense noise exposure. Immediately after noise exposure (4‐kHz octave band, 120 dB, for 5 hr), a population of hair cells exhibited calcineurin immunoreactivity at the cuticular plate, with a decreasing number of positive‐stained cells on Days 1–3. By Day 7, the levels of calcineurin immunoreactivity had diminished to near control, non‐noise exposed values, concomitant with an increasing loss of hair cells. Staining of hair cell nuclei with propidium iodide (PI), restricted to calcineurin‐immunopositive cells, indicated breakdown of cell membranes symptomatic of incipient cell death. The local application of the calcineurin inhibitors, FK506 and cyclosporin A, reduced the level of noise‐induced auditory brain stem response threshold shift and hair cell death, indicating that calcineurin is a factor in noise‐induced hearing loss. The results suggest that calcineurin inhibitors are of potential therapeutic value for long‐term protection of the morphologic integrity and function of the organ of Corti against noise trauma.

Creatine and tempol attenuate noise-induced hearing loss

To define the role of free radical formation and potential energy depletion in noise induced hearing loss (NIHL), we measured the effectiveness of tempol (free radical scavenger) and creatine (enhances cellular energy storage) alone and in combination to attenuate NIHL. Guinea pigs were divided into four treatment groups: controls, 3% creatine diet (2 weeks prior to noise exposure), tempol (3 mM in drinking water 2 weeks prior to exposure), and creatine plus tempol and exposed to 120 dB SPL one-octave band noise centered at 4 kHz for 5 h. The noise-only control group showed frequency-dependent auditory threshold shifts (measured by auditory brainstem response, ABR) of up to 73 dB (16 kHz) on day 1, and up to 50 dB (8 kHz) on day 10. Creatine-treated subjects had significantly smaller ABR threshold shifts on day 1 and on day 10. Tempol alone significantly reduced ABR threshold shifts on day 10 but not on day 1. ABR shifts after combination treatment were similar to those in the creatine group. Hair cell loss on day 10 was equally attenuated by creatine and tempol alone or in combination. Our results indicate that the maintenance of ATP levels is important in attenuating both temporary and permanent NIHL, while the scavenging of free radicals provides protection from permanent NIHL.

Bcl-2 Genes Regulate Noise-Induced Hearing Loss

Proteins of the Bcl‐2 family have been implicated in control of apoptotic pathways modulating neuronal cell death, including noise‐induced hearing loss. In this study, we assessed the expressions of anti‐ and proapoptotic Bcl‐2 genes, represented by Bcl‐xL and Bak following noise exposures, which yielded temporary threshold shift (TTS) or permanent threshold shift (PTS). Auditory brainstem responses (ABRs) were assessed at 4, 8, and 16 kHz before exposure and on days 1, 3, 7, and 10 following exposure to 100 dB SPL, 4 kHz OBN, 1 hr (TTS) or 120 dB SPL, 4 kHz OBN, 5 hr (PTS). On day 10, subjects were euthanized. ABR thresholds increased following both exposures, fully recovered following the TTS exposure, and showed a 22.6 dB (4 kHz), 42.5 dB (8 kHz), and 44.9 dB (16 kHz) mean shift on day 10 following the PTS exposure. PTS was accompanied by outer hair cell loss progressing epically and basally from the 4‐kHz region. Additional animals were euthanized for immunohistochemical assessment. BcL‐xL was robustly expressed in outer hair cells following TTS exposure, whereas Bak was expressed following PTS exposure. These results indicate an important role of the Bcl‐2 family proteins in regulating sensory cell survival or death following intense noise. Bcl‐xL plays an essential role in prevention of sensory cell death following TTS levels of noise, and PTS exposure provokes the expression of Bak and, with that, cell death.

Clinicopathologic study of salivary duct carcinoma and the efficacy of androgen deprivation therapy

OBJECTIVE Salivary duct carcinoma is a rare and aggressive tumor of the salivary glands. The objectives of this study were to investigate the clinicopathological features of salivary duct carcinoma and to determine whether androgen deprivation therapy should be recommended. STUDY DESIGN AND METHODS The clinical records of seven patients diagnosed with salivary duct carcinoma between 2002 and 2012 were retrospectively assessed. Tumor specimens were examined for overexpression of human epidermal growth factor receptor 2 (HER2) and androgen receptor by immunohistochemistry. A case of androgen receptor-positive salivary duct carcinoma who received androgen deprivation therapy is presented. RESULTS Of the seven patients, 43% had recurrences and metastases, and the 5-year survival rate was 68.6%. All patients were androgen receptor-positive, and 71% were HER2-positive. One patient, a 66-year-old man with androgen receptor-positive salivary duct carcinoma, received oral bicalutimide for 14 months and practically all lung metastases disappeared. CONCLUSION Androgen receptor is often overexpressed in salivary duct carcinoma. Androgen deprivation therapy is safe and should be considered for patients with androgen receptor-positive salivary duct carcinoma.

Spindle cell carcinoma of the palatine tonsil : report of a diagnostic pitfall and literature review

Spindle cell carcinomas of the tonsil are very rare tumors. We present an additional case that occurred in a 58-year-old woman. She presented with a tumor of the right tonsil. Histologic sections of tonsillar biopsies suggested that this tumor was a squamous cell carcinoma. She underwent a transoral resection of the right oropharynx. The final diagnosis was spindle cell carcinoma. We emphasize the difficulties in diagnosing this type of tumor and discuss therapeutic approaches to this rare tumor, which shows little response to radiotherapy; the literature is reviewed. We offer this case study in an effort to increase awareness of this rare malignancy.

GJB2-associated hearing loss undetected by hearing screening of newborns.

The hearing loss caused by GJB2 mutations is usually congenital in onset, moderate to profound in degree, and non-progressive. The objective of this study was to study genotype/phenotype correlations and to document 14 children with biallelic GJB2 mutations who passed newborn hearing screening (NHS). Genetic testing for GJB2 mutations by direct sequencing was performed on 924 individuals (810 families) with hearing loss, and 204 patients (175 families) were found to carry biallelic GJB2 mutations. NHS results were obtained through medical records. A total of 18 pathological mutations were identified, which were subclassified as eight inactivating and 10 non-inactivating mutations. p.I128M and p.H73Y were identified as novel missense GJB2 mutations. Of the 14 children with biallelic GJB2 mutations who passed NHS, eight were compound heterozygotes and 3 were homozygous for the c.235delC mutation in GJB2, and the other three combinations of non-c.235delC mutations identified were p.Y136X-p.G45E/p.V37I heterozygous, c.512ins4/p.R143W heterozygous, and p.V37I/p.R143W heterozygous. These 14 cases demonstrate that the current NHS does not identify all infants with biallelic GJB2 mutations. They suggest that the frequency of non-penetrance at birth is approximately 6.9% or higher in DFNB1 patients and provide further evidence that GJB2 hearing loss may not always be congenital in onset.

Comorbidity of GJB2 and WFS1 mutations in one family

It is rarely reported that two distinct genetic mutations affecting hearing have been found in one family. We report on a family exhibiting comorbid mutation of GJB2 and WFS1. A four-generation Japanese family with autosomal dominant sensorineural hearing loss was studied. In 7 of the 24 family members, audiometric evaluations and genetic analysis were performed. We detected A-to-C nucleotide transversion (c.2576G>C) in exon 8 of WFS1 that was predicted to result in an arginine-to-proline substitution at codon 859 (R859P), G-to-A transition (c.109G>A) in exon 2 of GJB2 that was predicted to result in a valine-to-isoleucine substitution at codon 37 (V37I), and C-to-T transition (c.427C>T) in exon 2 of GJB2 that was predicted to result in an arginine-to-tryptophan substitution at codon 143 (R143W). Two individuals who had heterozygosity of GJB2 mutations and heterozygosity of WFS1 mutations showed low-frequency hearing loss. One individual who had homozygosity of GJB2 mutation without WFS1 mutation had moderate, gradual high tone hearing loss. On the other hand, a moderate flat loss configuration was seen in one individual who had compound heterozygosity of GJB2 and heterozygosity of WFS1 mutations. Our results indicate that the individual who has both GJB2 and WFS1 mutations can show GJB2 phenotype.